A U.S. Air Force Tunnel Boring Machine, at Little Skull Mountain, in the State of Nevada, U.S.A. It is tangible proof that the U.S. military has tunnel boring machines. There are many rumors of secret military tunnel systems in the western states, and elsewhere. If the stories are true, machines such as this one would be used to make them. Source: U.S. Department of Energy, Nevada Operations Office, photo number MX-027-30, 14 December 1982.